Explore topic-wise InterviewSolutions in .

The correct CHOICE is (a) SUANNDFROY

The explanation is: For ENCRYPTING a plain text using route cipher we USE a table having 5 columns as SHOWN below. Then we read down the columns to cipher the plain text.

S

A

N

F

O

U

N

D

R

Y

So the CIPHERED text becomes “SUANNDFROY”.

Correct option is (d) FUNFACTS

The best EXPLANATION: For DECRYPTION we REVERSE the process used in encryption. So we arrange the letters of cipher text from bottom right anti CLOCKWISE and then read the grid horizontally.

F

U

N

F

A

C

T

S

So the resulting plain text is “FUNFACTS”.

The CORRECT OPTION is (c) REDSAC

The explanation is: For decryption we reverse the process USED in encryption. So we arrange the LETTERS of cipher text down the columns and then read the grid horizontally.

R

E

D

S

A

C

So the resulting plain text is “REDSAC”.

Correct OPTION is (b) false

Explanation: The key of ROUTE cipher not only DEFINES the SIZE of grid but also the path that is to be followed. So longer the message is, the harder it BECOMES to guess the path.

Right OPTION is (b) false

Explanation: Rail fence is CIPHER is less secure than route cipher. It is because the key of route cipher not only DEFINES the size of the grid but ALSO the path that is to be followed.

Correct choice is (c) Rail fence cipher

Best explanation: ROUTE cipher is closely related to rail fence cipher. In rail fence cipher the PLAIN text is written in a zig ZAG fashion in a grid whereas in route cipher the plain text is written HORIZONTALLY.

Right option is (C) by following an imaginary pattern drawn on a grid

Best EXPLANATION: Route CIPHER is a transposition cipher. It encrypts the plain TEXT by following an imaginary pattern on a grid.

Right CHOICE is (c) transposition cipher

The best EXPLANATION: Route cipher is a transposition cipher. It falls under the category of transposition cipher as it encrypts the plain TEXT by REARRANGING its letters.

Correct option is (a) a transposition CIPHER that performs encryption by following an imaginary pattern on a grid

Easiest explanation - Route cipher is a transposition cipher. It ENCRYPTS the plain TEXT by following an imaginary pattern on a grid. This pattern can VARY from one VERSION of route cipher to others.

The correct OPTION is (a) SNONRAFUDY

For EXPLANATION: For encrypting a plain text using rail FENCE cipher we USE a table having the NUMBER of rows equal to key value as shown below. Then we read along the rows to get the ciphered text.

S

 

N

 

O

 

N

 

R

 

 

A

 

F

 

U

 

D

 

Y

So the ciphered text becomes “SNONRAFUDY”.

Correct option is (b) rail fence cipher

For explanation: In transposition cipher the LETTERS remain the same in CIPHERED and plain TEXT. Their position is only changed WHEREAS in substitution cipher the letters become different in ENCRYPTED text. So rail fence cipher will be the correct option.

Correct option is (B) False

Best EXPLANATION: One time pad CIPHER is one of the most secure traditional cipher as it is ALMOST impossible to CRACK. Rail fence cipher is not very hard to crack. Thus rail fence cipher is less secure than one time pad cipher.

The CORRECT choice is (b) SECMSG

The explanation is: For DECRYPTION we reverse the process used in encryption.

S

 

C

 

S

 

 

E

 

M

 

G

So the resulting plain text is “SECMSG”.

Right answer is (b) False

To explain: The number of COLUMNS in the table of rail fence cipher is always equal to the number of letters in the plain TEXT. It is independent of the GIVEN KEY value.

Correct ANSWER is (b) transposition CIPHER and SUBSTITUTION cipher

For explanation: There are two types of a traditional cipher. First is transposition cipher and the second is substitution cipher.

Correct choice is (d) Additive cipher

Explanation: In poly alphabetic cipher each SYMBOL of PLAIN TEXT is replaced by a DIFFERENT cipher text regardless of its occurrence. Out of the given OPTIONS, only additive cipher is not a poly alphabetic cipher.

The correct CHOICE is (b) TRANSPOSITION CIPHER

Explanation: There are two types of traditional ciphers- Transposition and SUBSTITUTION cipher. In transposition cipher the letters of the given data are SHUFFLED in a particular order, fixed by a given rule.

Correct answer is (a) by arranging the LETTERS in a zig ZAG fashion in a table

The explanation is: Rail fence cipher is a TRANSPOSITION cipher. It ENCRYPTS a GIVEN plain text by arranging the letters in a zig zag fashion in a table.

Right option is (c) TRANSPOSITION cipher

Easiest explanation - RAIL fence cipher is a transposition cipher. It falls under the category of transposition cipher as it encrypts the plain TEXT by rearranging its LETTERS.

Right answer is (c) ZIG zag cipher

The best explanation: RAIL fence cipher is also known as zig zag cipher. It is so because the plain text GETS ciphered by arranging the letters in a zig zag fashion.

Correct choice is (a) RAJ

Easiest explanation - We first CONVERT the KEYWORD and plain text into their corresponding matrix respectively. Then we MULTIPLY those matrix and take MODULO 26 of the resulting matrix to get the CIPHERED text.

The CORRECT answer is (a) invertible matrix

Explanation: A key matrix used for encryption in hill cipher must be invertible matrix. OTHERWISE it will be impossible to DECIPHER the MESSAGE.

The CORRECT ANSWER is (d) 6×6

The best explanation: HILL cipher USES a n x n matrix in order to cipher the plain text. In this case n=6 so a 6×6 matrix will be used.

The CORRECT answer is (a) SECRET

To explain: To decrypt the message we follow the REVERSE procedure. We first find the inverse of the KEYWORD matrix then multiply it with cipher matrix.

Correct option is (b) False

Easy EXPLANATION - Both HILL CIPHER and playfair cipher are less VULNERABLE to frequency analysis. But hill cipher is quite vulnerable to other FORMS of attack and thus less secure than playfair cipher.

Right choice is (b) HILL CIPHER

Easy explanation - Out of the given OPTIONS hill cipher is the HARDEST cipher to break using frequency analysis. ALTHOUGH it is quite vulnerable to other forms of attack.

The CORRECT choice is (C) a substitution based cipher in which substitution is performed over a block of letters

The best I can EXPLAIN: Poly graphic cipher is a type of substitution cipher in which substitution is performed over a block of letters. Hill cipher is an EXAMPLE of poly graphic cipher.

The correct option is (a) matrix MULTIPLICATION

Easiest EXPLANATION - Encryption of PLAIN text in playfair cipher is done using matrix multiplication. Then MODULO 26 of the resulting matrix is taken so as to GET the ciphered text.

The correct choice is (b) substitution CIPHER

Explanation: HILL cipher is a substitution cipher. It falls under the category of poly ALPHABETIC cipher as it uses multiple substitutions at different positions in order to cipher the plain text.

Correct answer is (c) MATRIX algebra

Explanation: Hill cipher uses matrix multiplication in order to encrypt the given plain text. So it REQUIRES prerequisite KNOWLEDGE of matrix algebra.

The correct ANSWER is (c) they are REPLACED by the letter of the same row at the CORNER of the rectangle defined by the original pair respectively

The best I can explain: If the letters in a pair does not appear in same row or COLUMN then they are replaced by the letters of the same row at the corner of the rectangle defined by the original pair respectively. The order of letters should be maintained.

Right option is (a) they are REPLACED by the letter appearing IMMEDIATELY below them respectively

The BEST I can explain: If the letters in a pair appear in the same column then they are replaced by the letters appearing immediately below them respectively. If the ELEMENT to be replaced appears at the corner of the column then we wrap around to the TOP side of that column.

Correct option is (b) AHQAPNPAFR

Easiest EXPLANATION - For encrypting the plain text using PLAYFAIR cipher we use a 5×5 table that is constructed by using keyword. Then we apply rules for ENCRYPTION in ORDER to get the ciphered text. Table is GIVEN as under-

Correct option is (b) a null is ADDED in between the LETTERS

Easy explanation - In PLAYFAIR cipher if the letters in a PAIR are identical then a null is added in between the letters. Any letter can be used as a null as LONG as that letter is not the one being repeated.

Right answer is (C) DOLLAR

The explanation is: To DECRYPT the message we FOLLOW the reverse procedure. The table is formed in the same manner. APPLYING this we get the plain text to be “DOLLAR”.

Right choice is (d) playfair cipher

For explanation: Poly GRAPHIC cipher is a TYPE of substitution cipher in which substitution is performed over a BLOCK of LETTERS. In diagram substitution, two adjacent letters are SUBSTITUTED simultaneously. Playfair cipher was the first diagram substitution cipher.

Right option is (c) Playfair cipher

For explanation: Out of the given OPTIONS playfair cipher is the hardest cipher to break USING frequency analysis. It is because it does not substitute LETTERS of the WORD individually but it encrypts them in pairs of two.

Correct answer is (c) VIGENERE table

For explanation: Encryption of plain text in playfair cipher is done using a 5×5 table. In this table, all the alphabets of the KEYWORD are arranged ROW wise by eliminating any duplicates then the REMAINING letters of the alphabet are placed. One of the alphabet has to be OMITTED in order to fit all the alphabets in the table.

The correct answer is (B) Wheatstone playfair CIPHER

Easy explanation - Playfair cipher is ALSO known by the name of Wheatstone playfair cipher. It is because it was DISCOVERED by Charles Wheatstone but was PROMOTED by Lord Playfair.

Correct answer is (B) false

Best explanation: Autokey CIPHER is harder to CRACK than VIGENERE cipher. It is because in autokey cipher the key is formed using the plain text itself whereas in vigenere cipher the key is independent of the plain text. This makes autokey cipher more SECURE.

Correct option is (a) KEPWSN

For explanation: For ENCRYPTING a plain text in autokey cipher we first add the keyword at the beginning of the plain text in order to obtain the key for encryption. Then we USE the VIGENERE table for making RESPECTIVE substitutions.

The CORRECT answer is (B) AUTOKEY cipher

Easy EXPLANATION - In transposition cipher and mono alphabetic cipher the number of letters remain same in ciphered and deciphered text. But in poly alphabetic cipher the number of letters are different. So here as autokey cipher is the only poly alphabetic cipher so it will be the answer.

Correct answer is (b) autoclave CIPHER

The best I can EXPLAIN: Autoclave cipher is an alternative name given to autokey cipher. It is because the encrypted text is formed using a key that is GENERATED from a message(PLAIN text) itself.